PITTSBURGH, Pa.--(BUSINESS WIRE)--Biological evidence is often a DNA mixture of two or more people. Forensic laboratories apply thresholds that simplify DNA data, which can reduce match statistics or discard evidence.
But sophisticated computing better preserves identification information, as shown in a recent study, "TrueAllele Casework on Virginia DNA mixture evidence: computer and manual interpretation in 72 reported criminal cases." This fifth TrueAllele validation article was viewed a thousand times in one month at the open-access PLoS ONE journal website.
When federal forensic DNA interpretation guidelines changed four years ago, higher stochastic thresholds rendered previously reported DNA evidence unusable. Rather than withdraw DNA from criminal justice, the Virginia Department of Forensic Science (DFS) had Cybergenetics reevaluate the data using TrueAllele.
Cybergenetics issued reports in 72 cases on 92 DNA mixtures, most containing 3 or 4 contributors. The validation study compares the reported computer match statistics with manual threshold methods on the same data.
TrueAllele gave an average match statistic of 113 billion on the cases. Manual stochastic threshold analysis averaged 140 – a billion-fold reduction. The computer could make DNA comparisons that were impossible or impractical using manual methods.
"There is no scientific reason to abandon informative DNA mixture evidence," says Dr. Mark Perlin, lead author and senior scientist at Cybergenetics.
The study showed that TrueAllele computer interpretation of DNA mixture evidence is sensitive, specific, precise, accurate and more informative than manual interpretation alternatives. Moreover, TrueAllele can determine DNA match statistics when threshold-based methods cannot.
"TrueAllele is a useful forensic tool," says DFS scientist and co-author Dr. Susan Greenspoon. TrueAllele was approved by the Virginia Forensic Science Board, and is now used by DFS to solve DNA mixtures. A presentation on the study was given at the 2013 American Academy of Forensic Sciences meeting in Washington, DC.
DNA evidence can implicate criminals and exonerate the innocent. TrueAllele computer interpretation more effectively preserves DNA evidence and match information, relative to manual threshold methods. Both prosecutors and defense attorneys may benefit from use of this validated computer technology to review complex DNA mixture evidence.
Cybergenetics develops patented TrueAllele technology that objectively interprets DNA evidence, providing computer systems and databases to crime labs, and expert witness services for criminal cases. The Pittsburgh-based company was founded in 1994, and is privately held.